Fig. 1

A simplified directed acyclic graph (DAG) evaluating potential causal relationships between conflict, DTP3 vaccination rates, and diphtheria outbreaks. The left arm of the DAG reflects how armed conflict may affect diphtheria outbreak risk via the WHO VPD Strategic Objective 1 [19], hypothesizing that conflict events may reduce vaccination rates, subsequently increasing the population’s susceptibility to diphtheria outbreaks. The right arm of the DAG indicates that conflict events might impact the risk of diphtheria outbreaks in a mechanism independent of reducing vaccination rates, such as population migration and crowding, or affecting the ability of areas to achieve the WHO’s VPD Strategic Objectives 2 and 3, which focus on disease surveillance and emergency response capacity [19]